I don't think there is currently any API property for mailbox delivery events (I could be wrong, though, as the MailEnable API guide is quite outdated) so the process actually involves editing certain config files.You can create a script to automate it all, but it will have to do it the hard way (without much API help, that is)...

You can use the system option provider to do this, specifically, the MEAOSO object or the MEWebmail.Options class. The current api guide does not document this however (or at least the one on the web site)